It is well known that there are many applications for mechanical donuts. Thus, for example, one particularly useful application is as rotatable supports for supporting conveyor belts in mining and aggregate handling. Typically, such a conveyor belt is "endless" and on its upper surface conducts the conveyed material from one position to another. Spaced apart longitudinally along the major axis of the conveyor are rotatable members such as axles positioned at right angles to such major axis and on each of which there are affixed a plurality of donut-like members that are spaced longitudinally along the axis of each such axle. When the belt is in motion, it rides on the donuts which, with the axles, rotate so as to support the belt while introducing a minimum of friction to impede its movement.
Many mined materials such as fossil fuels and mineral ores are notoriously abrasive. While the surface of the endless belt tends to sustain the major part of the abrasion since it directly contacts the conveyed materials, abrasive dust from the materials and other sources nevertheless tends to abrade the working surfaces of the donuts that are in contact with the underside of the belts. Accordingly, it has been necessary regularly to replace the donuts and/or assemblies of axles and donuts that are mounted thereon.
Typically, when donuts become worn, an entire assembly consisting of axle and donuts is replaced. In representative installations, this requires from two to six men one to three hours to remove an old axle assembly (often referred to as an idler) and replace it with a new one. Moreover, such replacement often must be made under hazardous conditions such as those in which men must be suspended high in the air to gain access to the assemblies which often are positioned at highly elevated locations such as from 30 to 100 feet above ground level. In addition, temporary support must be supplied for an otherwise supported section of the conveyor belt. Since typically, roller axles (idlers) are spaced 10 or more feet apart, a substantial length of temporarily unsupported belt must be temporarily supported while the axle is being replaced. Accordingly, serious problems occur when practicing currently practiced procedures.
Not only are there time-consuming and dangerous aspects of the currently practiced procedures for maintaining belts as described above, but once the axle with its donuts (idler) is removed, it usually is scrapped. While some idlers can be repaired, such repairs are time-consuming and costly. Thus, the common procedure for such repair involves the utilization of a hydraulic press to press off from the supporting axle the worn donuts. The axle must then be cleaned and prepared for the mounting of new donuts and the donuts must be pressed into place along the axis of the idler. Subsequently, the repaired idler must be installed in place of an existing idler when the latter requires replacement. In most situations, it has been found to be more expensive to repair a used idler than to purchase a new one.
In view of the foregoing, there has continued to be a need for a way to provide routine maintenance and replacement of worn idler parts easily and without having to replace an entire axle assembly.